Osteoporosis is an important healthcare problem. It is estimated that 24 million Americans are affected by osteoporosis and that osteoporosis led to $13.8 billion in healthcare costs in 1995. The risk of dying from hip fracture complications is the same as the risk of dying from breast cancer. For Caucasian females over 50, the risk of hip, spine, or distal forearm fractures is 40%. Osteoporosis is currently defined as a condition in which bone mineral density is greater than two standard deviations below the mean of a young healthy population.
Current techniques for screening individuals for fracture susceptibility are relatively inaccurate and/or pose risks to the patient. For example, the present preferred technique for diagnosis of osteoporosis is dual X-ray absorption (DXA), which measures the amount of mineral in the bone. In some patients, however, a low mineral content does not appear to lead to an increased risk of fracture. Additionally, DXA requires that the patient is exposed to ionizing radiation.
Osteoarthritis is another important health care problem. It has been estimated that 40 million Americans and 70 to 90 percent of persons older than 75 years are affected by osteoarthritis. The prevalence of osteoarthritis among men and women is equal, though its symptoms occur earlier in women. Risk factors include age, joint injury, obesity, and mechanical stress.
Studies suggest physio-chemical alteration of the articular cartilage surface is an early event in the pathogenesis of osteoarthritis. The changes involve physical damage to structural matrix proteins, mediated by physical forces and degradative enzymes.
Current techniques for diagnosing or ruling out osteoarthritis include taking an X-ray image of a joint, analyzing blood samples, and analyzing synovial fluid withdrawn from the joint with a needle. The diagnosis is largely clinical because radiographic findings do not always correlate with symptoms. An X-ray image of a joint may indicate osteoarthritis if a normal space between the bones in a joint is narrowed, an abnormal increase in bone density is evident, or if bony projections or erosions are evident. A blood sample may indicate osteoarthritis if byproducts of hyaluronic acid are present. Hyaluronic acid is a joint lubricant and the presence of its byproducts in the blood may indicate the lubricant's breakdown, a sign of osteoarthritis. Also, elevated levels of a factor called C-reactive protein, which is produced by the liver in response to inflammation, may indicate osteoarthritis. On the other hand, elevated levels of rheumatoid factor and so-called erythrocyte sedimentation rates may indicate rheumatoid arthritis rather than osteoarthritis. An analysis of synovial fluid withdrawn from the joint may indicate osteoarthritis if cartilage cells are present in the fluid. On the other hand, a high white blood cell count in the synovial fluid is an indication of infection, and high uric acid in the synovial fluid is an indication of gout.